Freshwater and saltwater fishing are some of the most popular outdoor activities in the United States and throughout the world. Caught fish are often kept alive by placing the fish in a bucket, livewell, or other container or closed system. In addition, live bait is often used for fishing and must be kept in a similar container prior to use. Because the volume of water is limited in these closed systems, an aeration pump is often installed to replenish dissolved oxygen levels in the water. While aeration systems may maintain oxygen levels in the water to sustain the fish, other contaminates may build up in the closed system and poison the fish. For example, waste products discharged by the fish may increase ammonia concentration in the water and may build to levels that will kill the fish despite an adequate level of dissolved oxygen in the water. Traditional methods to control ammonia in these types of closed systems include lowering the pH of the water or introducing new water to the system (that is, diluting the ammonia concentration).
In a conventional aquarium system, ammonia concentrations can be controlled to below toxic levels by maintaining high dissolved oxygen levels and including reactors that promote biological nitrification. However, in a fresh-caught fish or fish transportation system, the ammonia accumulation rate is faster than the ammonia oxidation rate by nitrification. Therefore, direct removal of ammonia from the water is necessary. Ammonia removal methods include ion exchange, adsorption, chemical neutralization, reverse osmosis, electrochemical reduction-oxidation, air stripping and precipitation (Boyer, 2014; Mook, Chakrabarti, et al., 2012; Peddie, van Teijlingen, et al., 2005; Bhatnagar and Sillanpää, 2011). Among them, the ion exchange process is suitable for fish wastewater applications as it is inexpensive, has an easy operational procedure, and is renewable, especially when using zeolite as the ion exchanger (Emadi, Nezhad, et al., 2001; Bergero, Boccignone, et al., 1994; Zhou and Boyd, 2014; Lopez-Ruiz and Gomez-Garrudo, 1994; Singh, Vartak, et al., 2004). There are many kinds of natural zeolite materials, including clinoptilolite and chabazite. Although clinoptilolite is more abundant and less expensive, chabazite has been reported to have higher ammonia removal efficiency (Aponte-Morales, Payne, et al., 2014). Zeolite traps ammonia and toxic heavy metals in aquaculture wastewater, and it has been intensively studied. Many factors, such as zeolite type, particle size, pretreatment, and wastewater type affect ammonia removal effectiveness (Ghasemi, Sourinejad, et al., 2016).
Accordingly, what is needed in the art is a user friendly, sustainable, cost-effective, and capable system and method for reducing the ammonia level in fresh and saltwater systems.